For self help, try these knowledgebase notes
PumperNickel creates a detailed log file of many actions. It is usually called ppn-main.log, and is in the same directory as the PumperNickel executable. Check the end of this log file for messages that may indicate cause of problems or failure.
In Internet Explorer, make sure you have friendly error messages turned off. Tools, Internet Options, Advanced, Show friendly HTTP error messages should be unticked. Internet explorer looks at a reply, and if it is 500 (meaning error), and if the error messages is under 400 bytes, it displays it's own (unhelpful) message. The real error message is then hidden. By turning this option off, you can see what PumperNickel is actually complaining about.
If you have changed any of the XSL template files, take a careful look at your changes, and make sure all the XML is still valid. For really tricky problems, use the saxon java parser to validate and process the xsl outside of PumperNickel.
PumperNickel creates many intermediate temporary files in the database\temp and template\temp and batch directories. These files, which are a mix of html files, xml files, batch files and text files can often indicate the step prior to the error. Sort the directory by date last modified to see the most recent output file.
PumperNickel makes many different database connections. Make sure the connection to your database is valid, and check it with another tool, such as the UDL editor for OLE DB. Look in \program files\common files\system\ole db\data links\ for this tool. The settings for your database connection are in settings.xml or database\tablemap.xml
PumperNickel has a gaurdian service called PumperNark. This service makes sure PumperNickel is always running, and restarts it if it is not currently running. The configuration file that controls PumperNark is in c:\winnt\pumpernark.ini